Effects of wall temperature on boundary layer stability over a blunt cone at Mach 7.99

Effects of wall temperature on stabilities of hypersonic boundary layer over a 7-degree half-cone-angle blunt cone are studied by using both direct numerical simulation (DNS) and linear stability theory (LST) analysis. Four isothermal wall cases with Tw/T0= 0.5, 0.7, 0.8 and 0.9, as well as an adiabatic wall case are considered. Results of both DNS and LST indicate that wall temperature has significant effects on the growth of disturbance waves. Cooling the surface accelerates unstable Mack II mode waves and decelerates the first mode (Tollmien–Schlichting mode) waves. LST results show that growth rate of the most unstable Mack II mode waves for the cases of cold wall Tw/T0=0.5 and 0.7 are about 45% and 25% larger than that for the adiabatic wall, respectively. Numerical results show that surface cooling modifies the profiles of rdut/dyn and temperature in the boundary layers, and thus changes the stability haracteristic of the boundary layers, and then effects on the growth of unstable waves. The results of DNS indicate that the disturbances with the frequency range from about 119.4 to 179.1 kHz, including the most unstable Mack modes, produce strong mode competition in the downstream region from about 11 to 100 nose radii. And adiabatic wall enhances the amplitudes of disturbance according to the results of DNS, although the LST indicates that the growth rate of the disturbance of cold wall is larger. That because the growth of the disturbance does not only depend on the development of the second unstable mode

Direct numerical simulation of hypersonic boundary layer transition over a blunt cone with a small angle of attack

The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors’ previous work [Li et al., AIAA J. 46, 2899(2008)], the whole boundary layer flow over the cone is simulated (while in the author’s previous work, only two 45° regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 0° ≤ θ ≤ 30° (θ = 0° is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition location. Very low frequency waves VLFWs� are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough.The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors’ previous work [ Li et al., AIAA J. 46, 2899 (2008) ], the whole boundary layer flow over the cone is simulated (while in the author’s previous work, only two 45° regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 20° ≤ θ ≤ 30° (θ = 0° is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition location. Very low frequency waves (VLFWs) are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough

第三方购买、内部市场与过度医疗——基于不完全信息的动态博弈视角

在不完全信息动态博弈框架下,分析基于＂第三方购买＂构建的＂内部市场＂对纠正过度医疗的影响机制发现：（1）当某种疾病发病率较高且一旦发病,病情严重的概率也较高时,混同均衡占优;（2）＂内部市场＂构建后,引入保险机构作为独立的第三方,对医治过程实施监督抽查能显著降低混同均衡出现的概率,减少医生欺骗行为;（3）数值模拟结果表明混同均衡成立时临界值上升的幅度随病症轻重程度的变化呈现显著的＂倒U型＂,整体而言,＂内部市场＂降低了医疗资源误置,对轻症过度医疗的抑制效应显著高于重症,对住院过度医疗的抑制效应强于门诊。本文据此设计了一个兼顾医生、患者、医疗保险费收集者、医保基金公司等各方利益且充分利用市场机制的新医保体制。国家社科基金重大项目“需求结构转换背景下提高消费对经济增长贡献研究”（15ZDC011）;国家社科基金青年项目“供需均衡视角下的中国潜在经济增长率测算与增长要素分析”（16CJL011）的阶段性成

丙氨酰谷氨酰胺注射液的临床应用调查及合理性评价

目的调查某院丙氨酰谷氨酰胺注射液的使用情况,评价其合理性,以促进临床合理使用。方法调取某院2017年7—12月所有住院使用丙氨酰谷氨酰胺注射液的2 357份病历并统计分析,随机抽取每月30份共180份病历进行合理性评价。结果该院丙氨酰谷氨酰胺使用率为4.7%,使用金额占药品总金额的0.84%。180份点评的病历不合理率为27.2%,主要存在无适应证用药(61.2%)和给药剂量不合理(30.6%)。结论丙氨酰谷氨酰胺的使用存在一定的不合理性,建议制定合理使用规范加强管理,促进临床合理用药

基于校园卡身份识别系统架构与管理实现

目前校园一卡通身份识别系统普遍存在功能单一、容量小、扩展性差和兼容性差等问题.针对这些问题,运用物联网、虚拟化和分布式技术,结合高校的实际需求,在系统架构设计层面进行整体规划,建设一套集门禁、无线门锁、宿管、考勤和会签等功能于一体的综合性管理系统.实际使用证明,该系统易扩展,兼容性高,能为校园管理带来很多便利,并给学校管理决策提供多方位的参考依据

A New High Order Accurate Shock Capture Method with Wave Booster

A new kind of shock capturing method is developed. Before applying the high order accurate traditional scheme which is called as base scheme in this paper the fluid parameters are preconditioned in order to control the group velocity. The newly constructed scheme is high order accurate, simple, has high resolution of the shock, and less computer time consumed

内部控制、政府控制与财务报表重述

近年来,财务报表重述一直受到学术界和监管部门的广泛关注(GA0,2002,2003)。本文利用2007-2009年我国上市公司的数据研究了内部控制对财务重述的治理作用。研究发现:内部控制质量与财务重述显著负相关,内部控制质量越高,越不容易发生财务重述行为,表明内部控制是公司治理财务重述行为的有效措施之一;非政府控制公司的内部控制对财务报表重述具有治理作用,而政府控制公司的内部控制则没有这种治理作用。这可能表明政府控制公司的内部控制"摆设性"更强

Complicated reactive muffler design on wheel excavator

针对某型轮式挖掘机发动机排气噪声的频率组成分布在低中高全频段的特点,根据共振腔消声器和扩张室消声器这两种基本消声单元结构特性,提出了一种恰当结合两种基本消声单元结构进行复杂结构抗性消声器设计的方法,使得消声器在全频段具有良好的消声效果,运用gT-POWEr仿真软件对挖掘机发动机和消声器进行了耦合仿真,预测了复杂结构抗性消声器的性能,利用正交实验的方法对消声器内部结构参数进行了优化,最后通过实车测试进行了验证。实验及研究结果表明,所设计的复杂结构抗性消声器声学性能和空气动力性能良好,发动机排气噪声在全频段均有所下降,消声器插入损失平均达到18 d b(A),压力损失在许可范围内。Aiming at the analysis of wheel excavator engine exhaust noise that has a wide frequency,based on the structural characteristics of resonant cavity muffler and expansion chamber muffler,appropriately combine these two basic anechoic unit structure to design complex structure muffler,ensure the muffler has a good silencing effect in all frequency.GT-power simulation software was used to realize the coupling simulation of engine and muffler,and predict the performance of complex structure muffler.Orthogonal experiment was used to optimize the structure parameters of muffler.In the end,achieve expected results through vehicle tests.The results indicate that the muffler has a great acoustic performance and aerodynamic performance with the insertion loss 18 d B(A)in average.国家科技支撑计划资助项目(2013BAF07B04); 福建省自然科学基金计划资助项目(2014J01210); 深圳市知识创新计划资助项目(JCYJ20140417162429675

绿色荧光蛋白标记的CY15瘤细胞眼前房移植瘤早期转移的观察

[目的]观察绿色荧光蛋白（GFP）标记的恶性组织细胞增生症CY15细胞在Balb/c鼠眼前房生长及全身转移的规律,探讨GFP作为活细胞标记追踪肿瘤细胞生长、转移的优势并初步探讨肿瘤转移的机制.[方法]将携带绿色荧光蛋白的逆转录病毒MP71-GFP-PRE转入CY15细胞,G418筛选阳性克隆.20只Balb/c小鼠（20只右眼）,手术显微镜下每只小鼠眼前房接种2μL细胞密度为2.0×10^6个/mL的CY15GFP细胞悬液.术后15 d、20 d和30 d分别处死5只小鼠在荧光显微镜下观察全身转移情况.采用流式细胞仪分析术后30 d处死的另外4只小鼠和4只对照小鼠外周血单个核细胞中瘤细胞的比率.[结果]稳定表达绿色荧光蛋白的CY15GFP细胞基本保持了亲代细胞的特征,在前房的成瘤率为100%.术后15 d处死小鼠在荧光显微镜下观察可见肝、肺、胃肠壁等多个脏器中有散在的单个荧光点分布,为转移的单个肿瘤细胞,这些荧光点在肝脏中分布的数量最多.术后20 d、30 d分别处死5只小鼠,发现随着时间的推移这些微小转移灶逐渐增大.流式细胞仪分析术后30 d处死的小鼠外周血单个核细胞中瘤细胞的平均比率为0.048%±0.021%.[结论]绿色荧光蛋白标记瘤细胞后,利用荧光显微镜能有效地观察到肿瘤发生远距离转移在继发脏器中分布的单个瘤细胞和普通显微镜下无法分辨的微小转移灶,这些微小转移灶逐渐增大,为肿瘤转移的克隆起源学说提供了有力的证据.流式细胞仪能准确定量瘤细胞在外周血中的分布情况

Application of the three-dimensional visualization and 3D printing technology for the preoperative evaluation of retroperitoneal tumors

目的探讨三维重建及3D打印技术在腹膜后肿瘤术前评估中的应用价值。方法回顾性分析2011年3月至2015年9月厦门大学附属成功医院收治的50例腹膜; 后肿瘤病人的临床资料,应用人体器官三维建模软件将病人的CT二维图像重建成三维可视化图像,使用人体器官模型3D打印设备,用两色热塑性塑料打印实物模; 型,通过观察肿瘤与腹腔器官、腹部大血管之间的关系进行术前评估并制定手术方案。实施手术,术中比较重建结果与实际的区别。结果50例病人均成功完成三维; 重建,其中10例病人完成3D打印,三维重建结果及3D打印模型能够立体、清晰和实物化的显示肿瘤解剖学位置及与周围器官、血管的毗邻关系,与术中实际情; 况大致相符。50例病人均顺利施行手术,术中无死亡。结论三维重建及3D打印技术能够对腹膜后肿瘤术前进行精准评估,对指导手术具有一定的应用价值。Objective To explore the application value of three dimensional; visualization and 3D printing technology in the preoperative evaluation; of retroperitoneal tumors. Methods March 2011 to September 2015,the; clinical data of 50 cases of retroperitoneal tumor patients in Xiamen; University Affiliated successful hospital were retrospectively analyzed.; Xiamen strong science and technology R & D human organ 3D modeling; software will reconstruct 2D CT image visualization into a; three-dimensional visualization image,and then it can print physical; model with the company's XMQB-I human organ model 3D printing equipment; and white thermoplastic. At last,preoperative evaluation and surgical; plan can be made through the relationship between the tumor,organs in; abdominal cavity,and abdominal vascular. During the surgery,make a; comparison between the visualization results with the actual condition.; Results 50 cases of patients were successfully completed the; three-dimensional visualization,including 10 cases of patients; completed. Three-dimensional visualization and 3D printing model can; three-dimensionally,clearly show the adjacent relationship between the; anatomical tumour location and surrounding organs and blood; vessels,broadly in line with the actual surgery. 50 surgeries were; successfully performed,no death during perioperative period. Conclusion; Three dimensional visualization and 3D printing technology can make an; accurate preoperative evaluation of retroperitoneal tumors,which has a; certain application value for guiding surgery.国家自然科学基